From eBay; sepia tone removed by gogm.
The Princess wears a ca. 1820-style dress with an off shoulder bateau neckline adorned with a lace bertha. While a waist band cannot be seen, her dress waistline is above her natural waist. Her dress also has a significant train. See the next image.
Keywords: 1819, Beechey, Reynolds - Samuel, Princess Augusta Sophia, Princess, Welf family, British, neo-hurluberlu coiffure, feathered hat, draped necklace, off shoulder bateau neckline, lace bertha, Empire waistline, close skirt, train, lace-edged wrap